chore: add high level classes

Signed-off-by: The one with the braid <the-one@with-the-braid.cf>

README.md

@@ -6,8 +6,35 @@ A Dart native pkpass parsing library
 
 - no platform specific dependencies - pure Dart
 - parse any .pkpass file as blob
+- checksum verification
 - extract metadata
 - high level lookup for assets by locale and scale, with proper fallbacks
+- high level barcode API
+- No dependency on `dart:io` or `dart:ui` runs everywhere, from CLI to Flutter
+
+## Not supported (yet)
+
+Some parts of the PkPass specification are either not yet implemented, or not planned, such as:
+
+- `signature`: The detached PKCS #7 signature using Apple certificates of the manifest. Note: Checksums _are_ checked. -
+  Not planned, feel free to contribute.
+- `nfc`: Card payment information for Apple Pay. - Not planned, feel free to contribute.
+- `webService`: Information used to update passes using the web service. - Planned, feel free to contribute.
+
+## Dependencies and compatibility
+
+Any package should keep its dependencies as minimal as possible. Sometimes, there are specifications making this
+difficult. The PkPass spec unfortunately is a very complex one, requiring support of many standards and formats.
+
+The following dependencies are used to correctly parse the PkPass file into a relevant Dart representation.
+
+- [`pub:archive`](https://pub.dev/packages/archive): The PkPass file itself is a ZIP archive, used to parse the raw
+  bytes.
+- [`pub:barcode`](https://pub.dev/packages/barcode): Used to provide high-level access to barcode generation with the
+  proper encoding supported.
+- [`pub:crypto`](https://pub.dev/packages/crypto): Used for SHA1 signature verification as defined in the PkPass spec.
+- [`pub:intl`](https://pub.dev/packages/intl): Used for localization lookup of localizable resources like Strings or
+  assets.
 
 ## Getting started